1. Field
Antenna systems, such as an active antenna system (AAS), can include active and passive electronic components located closely together inside an antenna system. Such systems may benefit from variable adaptation of active antenna system radio frequency signal filtering.
2. Description of the Related Art
International Telecommunication Union (ITU) requirements describe only worldwide applicable requirements in respect of radio emission. Radio system specific requirements are described by other organizations, such as the 3rd Generation Partnership Program (3GPP). Radio system specific requirements can include long term evolution (LTE), wideband code division multiple access (WCDMA), global system for mobile communication (GSM), and the like. National specific requirements can also be added on to those requirements. For example, the British telecom regulator, Ofcom, has released additional radio requirements for co-location of mobile communication with national Digital Terrestrial Television (DTT) services. For other countries, like the United States, Germany, and so on, other additional requirements may likewise be defined.
In an active antenna system (AAS), variable RF filtering/RF combining may be used. AAS is a system architecture introduced in mobile radio communication. It can be viewed as an evolution from previous base transceiver station (BTS) design, for example remote radio head (RRH). Within RRH design, antenna and active part/passive part are not inseparably connected. Thus, an additional filter part can be easily placed.
FIG. 1 illustrates additional filtering in case of a remote radio head (RRH). As shown in FIG. 1, the remote radio head can include an active part/passive part 120 inside sealed outside enclosure 110. The sealed outside enclosure 110 can include inputs and outputs, such as a supply voltage 130, a data line with data to be transmitted 140, a data line with data received 150, and a control line 160 for control of the RRH. As used herein, the term “sealed” can refer to sealing in terms of ingress protection (IP), electromagnetic compatibility (EMC), not with respect to any desired radio frequency (RF) signals.
The remote radio head active part/passive part 120 can include, for example, baseband processing, up-/downconversion, filtering, radio frequency (RF) power amplification, low noise reception (RX) amplifier, and RF filtering, such as a diplex filter.
Also included can be an additional filter part 170 placed between the active part/passive part 120 and an antenna 180. The additional filter part 170 can include, for example, a bandpass/notch/lowpass filter. The additional filter part 170 can be connected to the active part/passive part 120 by an interface 190.
FIG. 2 illustrates an adaptive antenna system (AAS) setup. As shown in FIG. 2, the AAS can include a combination of an antenna radiator 220 and an active part/passive part 120. These elements can be combined in a compact way. However, as a result, an additional filter part cannot be inserted as in a conventional BTS design. For example, any additional filter part cannot be placed after the AAS itself, since the antennas are already an integral part of the AAS.
The AAS can include the active part/passive part 120 and the radiator part 220 inside sealed outside enclosure 110. The sealed outside enclosure 110 can include inputs and outputs, such as a supply voltage 130, a data line with data to be transmitted 140, a data line with data received 150, and a control line 260 for control of the AAS.
The active part/passive part 120 can include, for example, baseband processing, up-/downconversion, filtering, RF power amplification, a low noise RX amplifier, and RF filtering, such as a diplex filter or a triplex filter to inject another passive signal.
The radiator part 220 can include, for example, a passive antenna distribution network, an antenna matching network, and/or antenna radiation elements. Thus, the radiator part 220 can directly provide an external radio signal 225 without the need for any additional interface.
While the design is compact, in the above mentioned example, several different products may need to be designed and built for several different operators in one country. Moreover, different products may also be needed on a country-by-country basis.
FIG. 2 should be understood as not implying that there is a physical boundary between active part/passive part 120 and radiator part 220. Likewise, the drawing should not be understood as implying that subparts of each schematic section are physically arranged in the way shown. Subparts, as discussed herein, can refer to parts made of one or more elements to achieve a certain function.